There have been known collision simulation tests where a vehicle carrying a dummy simulating a passenger is actually driven into collision with an obstacle and damage caused to the vehicle and the passenger is evaluated. However, collision tests that employ actual vehicles and dummies are expensive and require a long preparatory period because the vehicle is destroyed and the dummy is damaged in each test. If a collision is simulated in a virtual three-dimensional space constructed on a computer using three-dimensional virtual models of a vehicle and a dummy, then the expenses and the preparatory period of such a collision simulation are greatly reduced.
When an impact is imparted to a virtual model of a vehicle and a virtual model of a dummy and their behaviors are analyzed on an impact/structure analyzing software program developed for analyzing a nonlinear phenomenon, problems arise in that parts which should collide with each other may move through each other or a part which will not actually be dented in may be dented in.
To solve the above problems and realize a simulation close to an actual collision, a conventional simulation apparatus performs a pre-processing operation called “collision definition” as disclosed in Japanese Patent Laid-open No. Hei 7-98772. According to the collision definition, conditions such as the hardnesses and materials of parts that are contacted upon a collision are preset, and the behaviors upon the collisions are simulated based on these conditions.
The conventional dummy described above is a virtual model of the dummy and has been developed for collision simulations for four-wheeled vehicles. Therefore, problems arise if the conventional dummy for a four-wheeled vehicle is applied directly to two-wheeled vehicles.
Specifically, as shown in FIG. 3, the conventional dummy has openings at upper arm ends 21, thigh joints 22, and a neck end 23 for keeping movable ranges of joints. Since there is no possibility for parts to contact those openings in collision simulations for four-wheeled vehicles, accurate results are obtained when those collision simulations are performed while ignoring such openings.
In collision simulations for two-wheeled vehicles, however, since the behavior of the rider differs widely from that of passengers on four-wheeled vehicles, as the rider may be thrown onto the road, parts may possibly contact the openings 21, 22, 23. On virtual models of conventional four-wheeled dummies, contact conditions cannot be defined for those regions because no face data are present in the above openings. Consequently, even when parts enter the openings in a collision simulation, no interference occurs therebetween, and they move through each other or are dented in. As a result, the behavior may not be converged and the simulation may be stopped, or even when simulation results are obtained, they may not be reliable enough.
Further, as shown in FIG. 10, a dummy model for four-wheeled vehicles has a reference posture with closed legs having both thighs 71R, 71L closed and knees bent at an obtuse angle.
However, two-wheeled vehicles require a normal riding posture with open legs having both thighs 71R, 71L sandwiching a fuel tank and knees bent at a sharp angle. Therefore, a dummy model for two-wheeled vehicles is needed to take a posture having both thighs spread, as shown in FIG. 11. If the dummy model for four-wheeled vehicles shown in FIG. 10 has its thighs 71R, 71L spread, then their attached ends kept in interference with the attached ends of the hip. Since the simulation apparatus is unable to perform normal calculations if contacting elements are present from the outset, the simulation apparatus fails to produce simulation results.
Spots of interference that occur when a four-wheeled vehicle dummy model takes a riding posture on a two-wheeled vehicle are not limited to the thighs and hip, but are present everywhere on the body, e.g., the thighs and lower thighs, the lower thighs and ankles, etc.
It is an object of the present invention to solve the conventional problems described above, and to provide a method of and an apparatus for performing a collision simulation on a two-wheeled vehicle using a virtual model of a dummy developed for use on four-wheeled vehicles. It is a further object to provide a method of generating a dummy model for two-wheeled vehicles based on a dummy model developed for use on four-wheeled vehicles.